The invention relates to a device to lift a denture model off a supporting plate with retention pins.
When a denture model is made, a patient""s negative mould is filled with liquid modelling material, e.g. plaster of Paris, and a supporting plate with retention pins is placed on the liquid modelling material so that the free retention pins extend into the modelling material as it hardens. The hardened denture model located on the supporting plate has to be removed from the supporting plate for processing and then replaced later, to prevent the supporting plate from being damaged when, for example, the denture model is cut into separate tooth or jaw segments.
The removal of the hardened denture model from the supporting plate, whether with or without simultaneous removal of the retention pins from the supporting plate, is often difficult, since the hardened modelling material adheres firmly to the supporting plate and the denture model is thus frequently damaged or even broken.
In DBGM 296 05 973, a device for lifting a denture model off its supporting plate is shown.
This device is described for supporting plates in which the retention pins remain in the supporting plate and are not lifted off with the denture model.
Here the device for lifting the denture model off the supporting plate consists of a flat separating section which rests on an additional piece moulded to the centre of the upper surface of the supporting plate. The outer edge of this separating section extends under the inner semicircle of the denture model from the inside.
The supporting plate with the additional moulded-don piece has a hole going through its centre, in which a nut is firmly anchored. This nut serves to hold a lift-off screw. When this screw is screwed in place, its end comes into contact with the flat separating section in which no hole has been drilled and thus lifts it off the rest of the supporting plate. Since the edge of the separating section extends under the denture model from the inside, the separating section takes the whole inner semicircle of the denture model with it and lifts it off the retention pins and supporting plate.
However, the disadvantage of the described device is that the denture model may easily tilt at the retention pins when being lifted off, since pressure is only applied in the middle and not at the places with the greatest adherence. Thus, when the denture model is lifted off the supporting plate, it may crack, e.g. through tensions in the plaster-of-Paris model, and may be damaged or broken.
This present invention tackles the problem of creating a device to lift a denture model off a supporting plate with retention pins, ensuring that, during the lifting-off process, this device exercises an even pressure directly at the places with the greatest adherence, namely directly where the retention pins, which may be either removable or non-removable, extend into the supporting plate, and thus avoiding any tilting or even breakage of-the body of the denture model.
The invention solves this problem with a device to lift a denture model off a supporting plate with retention pins with the features described in the patent claims.
Several alternative versions of the invention are explained and described in greater detail below with the help of drawings.
They show
FIG. 1 the top view of a supporting plate with inserted retention pins and openings, of approximately natural size,
FIG. 2 a semicircular fitting element, of approximately natural size,
FIG. 3 a side view of a supporting plate with a denture model on it and a lift-off plate, with a fitting element positioned between them, of approximately natural size,
FIG. 4 a side view of a supporting plate with a denture model on it, retention pins projecting from the bottom of the supporting plate and a lift-off plate, of approximately natural size
FIG. 5 a supporting plate with a denture model on it, retention pins projecting from the bottom of the supporting plate, a lift-off plate and a U-shaped clamp, of approximately natural size, and
FIG. 6 a side view of a supporting plate with a denture model on it and an indentation at the bottom, from which the retention pins project, and a lift-off plate with an elevation on the top, of approximately natural size.